The prior art teachings relating to light reflective signaling and warning devices include a metal propeller with a spiral pattern of fluorescent paints applied to one surface thereof intended especially for use on the rear of a bicycle, as described in U.S. Pat. No. 2,701,540 issued Feb. 8, 1955. As illustrated and described, this device would reflect light toward sources of light located over most of the surface of a reference hemisphere to the rear of the bicycle on which it is mounted, but not toward the front of the bicycle. In addition, any substantial deflection of this metal propeller would be permanent and tend to diminish or destroy its utility.
In column 1, lines 19 through 37 thereof, U.S. Pat. No. 3,684,348 to Rowland traces the long history of interest in the development of retroreflective materials, that is, materials capable of reflecting the bulk of the light rays impinging thereon along a substantially parallel path toward the source of the light, citing U.S. patents dating from 1906 concerned with the use of cube corner reflectors and referring to the flexible material comprising minute glass spheres embedded in a thin matrix of synthetic resin and sold under the trademark SCOTCHLITE by Minnesota Mining and Manufacturing Company.
Hereinafter, the term "retroreflecting" is to be understood and interpreted as referring specifically and only to " . . . materials capable of reflecting light rays impinging thereon along a substantially parallel path toward the source of the light . . . ," an important feature of the rotatable element incorporated in the instant invention, as compared to the many materials variously employed in the class of light reflective devices and merely described as "reflective" rather than as being "retroreflecting".
The light retroreflective material described and claimed in U.S. Pat. No. 3,684,348 to Rowland, manufactured as described and claimed in U.S. Pat. No. 3,810,804 to Rowland, lends itself especially well to incorporation in the instant invention, because of its high degree of flexibility, and preferably includes as its damage resistant front face a flexible light transparent sheet material having a thickness of 0.002-0.030 inch and preferably about 0.003-0.010 inch thick, to the rear face of which is adhered a continuous array of cube corner formations preferably each having side edge dimensions not more than 0.010 and most desirably on the order of 0.004-0.008 inch.
The Rowland light retroreflective material is also particularly well suited to use in the instant invention because it is understood to be about four times as reflective as any comparable material presently available, at least in part accounting for the results obtained in a test of the present invention in comparison to adjacent electric lights on a vehicle under actual operating conditions, which test is described further below under the heading, OPERATION OF THE PREFERRED EMBODIMENT.